This invention relates to methods and circuitry for testing electromagnetic devices and more particularly to a novel method and circuitry for testing electromagnetic actuators even while they are in service, while allowing effective control intervention during such testing.
Electromagnetic devices, such as solenoids, relays, contactors, electrovalves and the like, are normally tested before installation. However, there is no assurance that devices passing the test will operate for any determinable length of time in its actual environment of controlling circuitry and equipment loading. Equipment which uses such electromagnetic actuators in a critical application or protection function may be damaged, destroyed or rendered ineffective if the actuator fails to operate in the desired manner. One example would be a power supply, in which relay contacts are connected in series with the output and are actuated to open and break the connection when a load draws a current in excess of a certain percentage above a set maximum working current. The failure of that relay to actuate, when a control signal causes current to flow in an electromagnetic coil, will result in excessive heating and potentially permanent damage of the components. The non-functioning equipment must be repaired or replaced. In either case, the equipment is out of service for some amount of time.